arises in Grand Unified Theories and is expected to mediate the decay of the proton

Y

1

−1/3

about 1015

yes

yes

yes

—

The fundamental particles of matter*

The fundamental particles of matter*

particle

spin

electric charge

approximate mass

color

flavor

leptons

e

1/2

−1

1/2,000

no

yes

ne

1/2

0

0

no

yes

m

1/2

−1

1/10

no

yes

nm

1/2

0

0

no

yes

t

1/2

−1

2

no

yes

nt

1/2

0

0

no

yes

quarks

u

1/2

2/3

1/50

yes

yes

d

1/2

−1/3

1/100

yes

yes

c

1/2

2/3

2

yes

yes

s

1/2

−1/3

1/5

yes

yes

t

1/2

2/3

>18

yes

yes

b

1/2

−1/3

5

yes

yes

*The attributes color and flavor have precise technical meanings in particle physics (see text). The masses of the particles vary over a wide range and are expressed relative to the mass of a proton as a convenient
unit. The electric charge is relative to that of the proton. Spin is the angular momentum resulting from the rotation of a
particle on its axis. For each particle there is an antiparticle with opposite electric charge, color, and flavor; the antiparticles
are not listed separately.

Related resources for this article

Introduction

Scientists have increasingly developed techniques to probe ever more deeply into the structure of matter and to break down matter into its most basic elements. The concept of the atom has existed since the 5th century bc, but it was not until the beginning of the 19th century that this concept was developed into a scientific theory. Almost as soon as the modern atomic theory was established, it was discovered that atoms were not…

Constituents of Matter

Properties of Atomic Particles

Evidence of a New Particle

Unifying the Forces of Nature

Additional Reading

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